In recent years, there is known a CEP (complex event processing) as a technique for processing many items of data always corrected from various objects in parallel. With the complex event processing, an event is detected for received data and a processing for the detected event is performed. The complex event processing may be called ESP (Event Stream Processing), but is generally called CEP including ESP herein.
In the CEP system that performs a complex event processing, a large amount of received data may be temporarily processed, and thus a processing load may increase and a processing capability may decrease. Since the CEP system processes data in real-time, the CEP system is expected to be always running, and is not allowed to be stopped.
Thus, in the CEP system, a system technique capable of flexibly allocating resources used for cloud and the like is used to distribute processings into a plurality of servers or virtual machines (VM) according to a variation in processing load. For example, a processing request sentence called query and data associated with the query, which are arranged in a server or virtual machine with a high processing load, are moved as processing elements to other servers or virtual machines to distribute the processings.
Patent Literature 1: Japanese Laid-open Patent Publication No. 2005-258552
However, in the CEP system, when the processing elements are moved, a processing of a query as a processing element to be moved is stopped, which causes a delay in the data processing.